This invention relates to an improved cardiac sling for supporting the heart and providing cardiac exposure for surgery to the circumflex branch of the coronary artery.
Coronary bypass surgery of the circumflex coronary artery is difficult because the vessel lies on the posterior surface of the heart. The field is made accessible by arresting and draining, and then lifting and partially rotating the heart. Several methods have been used to achieve the required exposure. An assistant may hold the heart with outstretched hand. This can be inconvenient for several reasons. Of importance is that an assistant is required. In some cardiac centers, where an assistant is not used, this method is inappropriate. The assistant's hand in the operative field can get in the way, and the assistant, who often stands adjacent to the surgeon, may restrict the surgeon's movements. The assistant often does not have a clear view of the heart, and often finds the process tiring. The heat from the assistant's hand will warm the hypothermic heart in the area of digital pressure. This digital pressure can cause bruising of the heart.
The use of a neat was described by R. W. M. Frater, "Yet another technique for exposing the circumflex coronary artery" Am. J. Surg. 133, 650-651, 1977. This method has the merit of low cost, but the fine strands impinge on the heart and potentially can cause damage.
A heart support for coronary artery surgery was described in U.S. Pat. No. 3,983,863 (Janke, W. H. and Barron, M.). This heart support was formed of flat clotch tapes crossing each other at right angles and attached together to provide a mesh with square openings. The disadvantage of this device is that the cloth has a rough texture that can abrade the heart. The device is relatively inelastic, and cannot therefore support the heart in a uniform manner. In addition, the squares formed between the tapes are rather large, while the area of the heart lying under the tapes are not visible to the surgeon.
A later device was described by Angelini, G. D. "A simple, inexpensive method of heart retraction during coronary bypass surgery" Ann. Thorac. Surg. 46, 246, 1988. The method has the merit of simplicity, low cost and good exposure, but has the disadvantage that the supported weight of the heart is carried over a small area, which may cause damage to the myocardium.
A further consideration in coronary artery surgery is hemorrhage from the incision into the coronary artery at the proposed anastomotic site. Coronary artery surgery is usually carried out under conditions of cardiac arrest and aortic root cross clamping. Hence the myocardium is temporarily deprived of coronary blood supply. In some patients, an additional coronary blood supply, through to be from bronchial circulation, causes significant hemorrhage during the bypass grafting process. This hemorrhage is both inconvenient, as it masks the surgeon view during the delicate suturing process, and threatens the well-being of the patient.
An objective the present invention is an improved cardiac sling providing a substantially uniform support over the contacted surface of the heart.
A further objective of the present invention is to provide an unobstructed view of the heart to the surgeon.
A further objective of the present invention is to constrict unwanted coronary circulation to minimize hemorrhage from the anastomotic site during coronary bypass grafting.